1. Field of the Invention
The invention relates to a device for the centerless grinding of rotation-symmetrical surfaces on work pieces, including a drive to turn the workpieces about their axes of symmetry while they are being ground and while they are supported on a support bar; two rotating discs disposed on both sides of, and crosswise to, the work piece, at least one of which being a grinding disc working under grinding pressure; and mechanical bearing supports and feed means for the discs. The discs can be two grinding discs. However, one grinding disc and one control disc may also be provided. The workpieces may be elongated cylindrical workpieces which are not only turned during the grinding but also advanced in the longitudinal direction. They may also be shorter work pieces which can also have sections of different diameter. Also included is a feature of cutting-off by means of cutting-off discs.
2. Description of the Prior Art
In all these operations, vibrations of operating frequencies are generated at the grinding station. On the other hand, the mechanical bearing supports and feed means for the disc together form an oscillating system. It frequently happens that this oscillating system is excited to resonance vibrations by the operating frequencies, whereby vibrations with so high an amplitude can occur that undesirable markings are formed on the surface of the work pieces. In order to avoid this, the bearing supports for the discs have already been equipped with large masses. This was based on the concept that the vibration would be reduced with a larger mass. The support for the bearings was then often constructed in the form of heavy swinging arms or heavy carriages on a sliding track. It has been found that the vibrations of the bearing supports and the undesired markings caused by these vibrations are not reliably eliminated thereby. It was determined by tests that the reason for this is that the hereinafore-mentioned heavy supports cause resonance frequencies for the vibrations of the disc bearings which are approximately at 60 to 80 Hz. These are frequencies which can be generated by the grinding and which then make the entire machine vibrate. If the masses serving to mount the disc bearings are increased further, the spring constant of the oscillating system given by the elasticity of the machine frame is generally also increased due to the mechanical construction, so that the reasonance frequencies with their detrimental accompanying phenomena remain substantially unchanged.